A theme green/blue based (NO LONGER SUPPORTED, YOU ARE FREE TO USE THE SOURCE CODE TO CREATE YOUR OWN THEME)
To install: Click on "Download ZIP" button
Extract the .theme.css archive
Go to \AppData\Roaming\BetterDiscord\themes (Windows only)
Paste
Reload Discord by pressing Ctrl + R
Go to the Configs, down to BetterDiscord and click "Themes"
Enable it
Enjoy